1. Field of the Invention
The invention is based on a process for producing a carbon-containing sintered compact from steel powder, in which the steel powder is heated to sintering temperature in an atmosphere containing, at least for a time, carbon monoxide, is kept at sintering temperature over a predetermined period of time, and the sintered compact formed thereby is subsequently cooled.
2. Discussion of Background
The invention relates in this respect to a prior art such as that specified, for example, in Metals Handbook Ninth Edition Vol 7 Powder Metallurgy, pages 360 and 361. In this prior art, a process for producing a sintered compact, in which steel powder is mixed with graphite powder and the resulting powder mixture is subsequently sintered, is described. The graphite is intended to have two effects here: firstly it is intended to reduce metal oxides in the steel powder, secondly it is intended to diffuse into the steel powder, in order thus to bring the carbon content of the sintered compact to a predetermined value. This is necessary since otherwise a considerable decarburization of the steel powder takes place in the atmosphere acting during sintering, which is frequently a vacuum or contains an inert gas. During this decarburization, the carbon in the steel powder escapes by reacting with oxygen, for instance from or on the grains of steel powder or from the atmosphere, to form carbon monoxide, which is generally flushed away or pumped away with the atmosphere. In order to avoid such decarburization, an extremely homogeneous and finely distributed mixture of steel and graphite powder is necessary. This requires complex technology and, in a production process set up for mass production, can scarcely be tested for the degree of distribution for the purposes of quality control.